改进的QuEChERS结合气相色谱-三重四极杆质谱法快速测定酸肉中10种挥发性N-亚硝胺类化合物

采用改进的QuEChERS方法进行提取和净化,建立了气相色谱-三重四极杆质谱(GC-MS/MS)快速测定酸肉样品中10种挥发性N-亚硝胺类化合物的检测方法。样品经乙腈提取和正己烷除脂后,采用十八烷基硅烷键合硅胶(C18)和N-丙基乙二胺(PSA)混合吸附剂净化,采用DB-WAX色谱柱(30 m×0.25 mm×0.25μm)分离,在选择反应监测(SRM)模式下进行测定,外标法定量。10种N-亚硝胺类化合物在1~100μg/L范围内线性关系良好,相关系数(r)均0.99。10种N-亚硝胺类化合物的加标回收率为79.8%~115.3%,相对标准偏差(RSD)为0.6%~22.9%(n=6);方法的检出限(LOD,S/N=3)和定量限(LOQ,S/N=10)分别为0.04~0.3μg/kg和0.1~1μg/kg。该法简便快速,灵敏有效,适用于酸肉中N-亚硝胺类化合物的快速筛查和测定。     

Wide-viewing-angle switchable image splitter obtained using varied-line-spacing H-PDLC Bragg grating

We propose the use of a varied-line-spacing (VLS) holographic polymer-dispersed liquid crystal (H-PDLC) Bragg grating as a switchable image splitter to generate a compatible three-dimensional (3D) stereogram and to increase the viewing angle of the observer. To fabricate the VLS grating, a cylindrical lens is adopted to form a cylindrical wave, which interferes with a plane wave, generating an H-PDLC grating with a continuously varying period. The proposed holographic optical element (HOE)-based image splitter comprises two VLS H-PDLC gratings. It can be attached on a designed pattern, with two rectangles taking the place of conventional liquid crystal display panel pixels, and can separate them into right and left viewing fields with a wider range. Experimental results show that the movement of the eyes of the observer can reach 37.6 mm. A theoretical simulation indicates that a shorter focal length of the cylindrical lens can yield a larger movement range. Switching between two-dimensional and 3D modes can be performed by applying an external alternating-current voltage at ~80 V. The contrast ratio of the diffracted images induced by crosstalk is greater than 60%, which indicates the feasibility of the proposed HOE for 3D image splitting.     

Comparison of Gasoline-Ranged <Emphasis Type="Italic">n</Emphasis>-Alkanes Conversions Using Dielectric Barrier Discharge: A Kinetic Study

Here, we compared the conversion of gasoline-ranged n-alkanes (C₆–C₉) using dielectric barrier discharge. For an energy density of ~68 J/L and an initial n-alkane concentration of ~230 ppm, when carbon number increased from 6 to 9, the energy efficiency of n-alkane conversion increased from 117 to 240 mmol/kWh, CO _x selectivity decreased from 46 to 20%, and ozone concentration increased from 216 to 240 ppm. The effect of energy density and initial n-alkane concentration were also investigated. The understanding of initial step of conversion was greatly aided by a proposed kinetic model. The pathways of consecutive reactions from the initiation to products were also discussed.     

Highly fluorescent carbon polymer dots prepared at room temperature,and their application as a fluorescent probe for determination and intracellular imaging of ferric ion

Carbon polymer dots (CPDs) were prepared by a one-pot aqueous synthetic route from ascorbic acid and diethylenetriamine at room-temperature. The CPDs under 350-nm excitation exhibit blue fluorescence peaking at 430 nm with a quantum yield of 47%. Other features include an average diameter of 5 nm, a fluorescence that is independent of the excitation wavelength, good water dispersibility and photostability, and excellent biocompatibility. The CPDs are shown to be viable fluorescent probes for ferric ion which acts as a strong quencher. The response to Fe(III) is linear in the 0.2 to 10 μM concentration range, and the detection limit is 0.1 μM. The probe was applied to the determination of Fe(III) in environmental waters and to intracellular imaging of ferric ions in HeLa cells.

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Graphical abstract Carbon polymer dots (CPDs) are prepared from ascorbic acid and diethylenetriamine (DETA) at room-temperature (RT). The RT-CPDs exhibit excellent optical performance, biocompatibility and selectivity of quenching by ferric ions. This can be applied for determination and intracellular imaging of ferric ion.

     

Salting-in/Salting-out Mechanism of Carbon Dioxide in Aqueous Electrolyte Solutions

The solvation of carbon dioxide in sea water plays an important role in the carbon circle and the world climate. The salting-out/salting-in mechanism of CO₂ in electrolyte solutions still remains elusive at molecule level. The ability of ion salting-out/salting-in CO₂ in electrolyte solution follows Hofmeister Series and the change of water mobility induced by salts can be predicted by the viscosity B-coefficients. In this work, the chemical potential of carbon dioxide and the dynamic properties of water in aqueous NaCl, KF and NaClO₄ solutions are calculated and analyzed. According to the viscosity B-coefficients, NaClO₄ (0.012) should salt out the carbon dioxide relative to in pure water, but the opposite effect is observed for it. Our simulation results suggest that the salting-in effect of NaClO₄ is due to the strongly direct anion-CO₂ interaction. The inconsistency between Hofmeister Series and the viscosity B-coefficient suggests that it is not always right to indicate whether a salt belongs to salting-in or salting-out just from these properties of the salt solution in the absence of solute.     

Exact controllability of nodal profile for 1‐D first order quasilinear hyperbolic systems with internal controls

For 1‐D first order quasilinear hyperbolic systems without zero eigenvalues, based on the theory of exact boundary controllability of nodal profile, using an extension method, the exact controllability of nodal profile can be realized in a shorter time by means of additional internal controls acting on suitably small space‐time domains. On the other hand, using a perturbation method, the exact controllability of nodal profile for 1‐D first order quasilinear hyperbolic systems with zero eigenvalues can be realized by additional internal controls to the part of equations corresponding to zero eigenvalues. Furthermore, by adding suitable internal controls to all the equations on suitable domains, the exact controllability of nodal profile for systems with zero eigenvalues can be realized in a shorter time.     

塞来昔布的密度泛函理论计算及光谱分析

塞来昔布(Celecoxib, CXB)是COX-2的高选择性抑制剂,经过20年的发展已经成为世界范围内使用最为广泛的一类处方药.本文基于密度泛函理论,使用B3LYP泛函,6-311++G(d, p)基组进行结构优化.在此工作上对该药物分子的结构、红外光谱、拉曼光谱、分子前线轨道、静电势和激发态性质做了一系列的研究.结果表明：CXB分子是一个稳定的非平面扭曲结构,此结构使得该药物分子在COX-2上的疏水通道中可以迅速通过,从而形成了一个可与苯磺酰胺片段结合的结合腔.对化合物进行频率计算,分别得到红外光谱和拉曼光谱,与实验采集的数据进行对比,呈现出较好的一致性.对分子的基态进行前线轨道和静电势的分析,磺酰胺基与COX-2易形成氢键作用.在CXB分子的激发态研究中发现,CXB分子的激发态性质主要由第1激发态、第3激发态和第6激发态共同决定.这为理解CXB的作用机理提供了重要的信息,也为后期扩展CXB衍生物提供了理论基础.     

空心NiCo2S4纳米球助催化剂担载ZnIn2S4纳米片用于可见光催化制氢

纳米片与空心球上之间的合理界面调控是开发高效太阳能制氢光催化剂的潜在策略。在各类光催化材料中,金属硫化物由于具有相对较窄的带隙和优越的可见光响应能力而被广泛研究。ZnIn₂S₄是一种层状的三元过渡金属半导体光催化剂,其带隙可控(约2.4 eV)。在众多金属硫化物光催化剂中,ZnIn₂S₄引起了广泛兴趣。然而,单纯的ZnIn₂S₄光催化活性仍然相对较差,主要是因为光生载流子的复合率较高、迁移速率较慢。在半导体光催化剂上负载助催化剂是提升光催化剂性能的一种有效方法,因为它不仅可以加速光生电子和空穴的分离,而且还可以降低质子还原反应的活化能。作为一种三元过渡金属硫化物,NiCo₂S₄表现出较高的导电性、较低的电负性、丰富的氧化还原特性以及优越的电催化活性。这些特性表明,NiCo₂S₄可以作为光催化制氢的助催化剂,以加速电荷分离和转移。此外,NiCo₂S₄和ZnIn₂S₄都属于三元尖晶石的晶体结构,这可能有助于构建具有紧密界面接触的NiCo₂S₄/ZnIn₂S₄复合物,从而提高光催化性能。本文中,将超薄ZnIn₂S₄纳米片原位生长到非贵金属助催化剂NiCo₂S₄空心球上,形成具有强耦合界面和可见光吸收的NiCo₂S₄@ZnIn₂S₄分级空心异质结构光催化剂。最优NiCo₂S₄@ZnIn₂S₄复合样品(NiCo₂S₄含量：ca. 3.1%)的析氢速率高达78 μmol·h^-1,约是纳米片组装ZnIn₂S₄光催化剂析氢速率的9倍、约是1% (w, 质量分数)Pt/ZnIn₂S₄样品析氢速率的3倍。此外,该复合光催化剂在反应中表现出良好的稳定性。荧光和电化学测试结果表明,NiCo₂S₄空心球是一种有效的助催化剂,可促进光生载流子的分离和传输,并降低析氢反应的活化能。最后,提出了NiCo₂S₄@ZnIn₂S₄光催化析氢的可能反应机理。在NiCo₂S₄@ZnIn₂S₄复合光催化剂中,具有高导电性的NiCo₂S₄助催化剂可快速接受ZnIn₂S₄上的光生电子,用以还原质子生成氢气,而电子牺牲剂TEOA捕获光生空穴,进而完成光催化氧化还原循环。该研究有望为基于纳米片为次级结构的分级空心异质结光催化剂的设计合成及其光催化制氢研究提供一定的指导。     

基于风险理念的黄土滑坡调查与编图研究

滑坡风险管理在国外已成为缓减地质灾害损失的重要手段,我国(香港地区除外)在滑坡风险管理方面起步较晚,尚处于探索阶段,目前正在开展的地质灾害详细调查项目尚没有很好地采用国际上流行的风险管理的理念和技术方法。本文以国土资源大调查部署实施的延安市宝塔区地质灾害详细调查示范项目为例,借鉴国际滑坡和工程边坡联合技术委员会制订的《土地利用规划滑坡易发性、危险性、风险区划指南》^[1] 及相关最新文献^[2~7],剖析了《滑坡崩塌泥石流灾害详细调查规范》和地质灾害详细调查项目实施中存在的问题及其与风险管理之间的差距。认为我国目前开展的地质灾害详细调查总体上属于中比例尺,还没有达到详细比例尺; 调查精度包括了高精度、中精度和低精度3种精度层次。提出了基于GIS、DEM、RS、地面调查等技术方法的黄土滑坡调查与编图的工作思路和技术路线。从1 :5万滑坡调查与风险编图、1 :1万滑坡调查与风险编图、村镇及重要基础设施滑坡调查与风险评估、典型滑坡点风险调查与评估4个方面,总结了基于风险管理理念的延安市宝塔区黄土滑坡调查与风险编图实例,旨在为《滑坡崩塌泥石流灾害详细调查规范》的修编和地质灾害详细调查项目更好地实施提供借鉴。